terça-feira, 28 de fevereiro de 2017

SOMETIMES the sun
burps. It flings off mighty arcs of hot plasma known as coronal mass
ejections (CMEs). If one of these hits Earth it plays havoc with the
planet’s magnetic field. Such storms are among the most spectacular
examples of what astronomers call space weather, a subject to which a
session at this year’s meeting of the American Association for the
Advancement of Science (AAAS), in Boston, was devoted. A big CME can
have profound effects. In 1859, for instance, a CME subsequently dubbed
the Carrington event, after a British astronomer who realised its
connection with a powerful solar flare he had observed a few days
earlier, generated auroras that could be seen in the tropics. Normally,
as the names “northern” and “southern” lights suggest, such auroras
(pictured above) are visible only from high latitude. More significant,
the Carrington event played havoc with Earth’s new telecommunications
system, the electric telegraph. Lines and networks failed, and some
operators received severe shocks.

Today, the damage would be
worse. A study published in 2013 by Lloyd’s, a London insurance market,
estimated that a Carrington-like event now would cause damage costing
between $600bn and $2.6trn in America alone. A year before this report
came out the sun had indeed thrown off such an ejection—though not in
the direction of Earth. A much smaller storm did, however, do serious
damage in 1989, by inducing powerful currents in Quebec’s grid, blacking
out millions of people. It would therefore be useful, Jonathan Pellish
of the Goddard Space Flight Centre, a NASA laboratory, told the meeting,
to be able to forecast space weather in much the same way as weather is
forecast on Earth. This would permit the most vulnerable equipment to
be disconnected, in advance of a CME’s arrival, to prevent damaging
power surges.

Sturm und drang

It sounds
straightforward enough, but is harder than it sounds. Though CMEs are
common, they cause problems on Earth only if they score a direct hit.
The so-called “empty” interplanetary space of the solar system is, in
fact, suffused by a thin soup of charged particles. These particles
interact with moving CMEs in ways that are hard to predict. That makes
forecasting a storm’s track difficult. On top of this, CMEs themselves
have magnetic fields, with north and south poles, just as Earth does.
The way the poles of a CME line up with those of Earth can affect the
intensity of the resulting electrical activity.

To try to
understand all this better a number of satellites already monitor the
sun, looking for, among other things, CMEs. These include a fleet of
American environment-modelling craft and also the Solar and Heliospheric
Observatory, which is a joint European-American venture launched in
1995. Several new sun-watching instruments are planned for the next
couple of years. One is the European Space Agency’s Solar Orbiter.
Another is NASA’s Solar Probe Plus. A third is a special telescope,
called DKIST, to be built in Hawaii. The eventual goal, said Dr Pellish,
is to make space-weather forecasts as easy and routine as terrestrial
ones.

Preparing for the extraterrestrial equivalent of hurricanes
in this way is surely wise. But space drizzle can cause problems too.
Even when the sun is quiet, Earth is bombarded by a steady stream of
high-energy subatomic particles. Some come from the sun, which is always
shedding matter in small quantities even when it is not throwing off
CMEs. Others are cosmic rays, which originate from outside the solar
system. Both types, when they smash through the atmosphere, create
showers of secondary particles in their wake. And, as Bharat Bhuva, an
engineer at Vanderbilt University in Tennessee, described to the
meeting, this shrapnel can cause problems with the electronic devices on
which people increasingly depend.

If such a particle hits a
computer chip, it can inject an electrical charge into the circuit.
Since chips work their magic by manipulating packets of charge, that can
create all sorts of problems. Dr Bhuva described how, in 2008, the
autopilot of a Qantas airliner had been knocked out by a rogue particle.
The resulting sudden plunge of about 200 metres injured many of the
passengers, a dozen seriously.

Subtler effects can be just as
worrying. During a local election in Belgium in 2003, a single scrambled
bit of information, almost certainly caused by an errant particle,
added 4,096 votes to one candidate’s tally. Since this gave an
impossibly high total, the mistake was easily spotted. But had the
particle hit a different part of the circuit it might have added a
smaller number of votes—enough to change the outcome without anyone
noticing. Moreover, as the components from which computer chips are
built continue to shrink, they become more sensitive, making the problem
worse. A modern computer might expect somewhere between a hundred and a
thousand space-drizzle-induced errors per billion transistors per
billion hours of operation. That sounds low. But modern chips have tens
of billions of transistors, and modern data centres have millions of
chips—so the numbers quickly add up.

The trick is to design
circuits to cope. That is where Christopher Frost, who works at the
Rutherford Appleton Laboratory, near Oxford, thinks he can help. He and
his team have modified some particle accelerators in a way that offers
designers of electronic equipment the ability to test their
products—and, crucially, to test them quickly. Dr Frost’s particle beams
are millions of times more intense than the radiation experienced by
real-world devices. They deliver in minutes a dose that would take years
to arrive naturally.

This sort of pre-emptive action makes sense.
The threats from space drizzle (constant, though low-level) and from
CMEs (rare, but potentially catastrophic) are real. Hardening equipment
against drizzle, and developing forecasts that tell you when to
disconnect it to avoid CME-induced power surges, are merely sensible
precautions.

This article appeared in the Science and technology section of the print edition under the headline "Tales of wonder"Source: The Economist